Stainless steel products, especially 18-8 stainless steel products containing about 18% of chrome (by weight; the same applies hereinafter) and about 8% of nickel have been becoming widely employed because of their superior corrosion resistance and processability. However, such products do not have quenching hardenability and also are not so superior in processing hardenability. Therefore, these products are not suitable for the use for parts demanding high wear resistance. It is common that martensitic stainless steel products, which have quenching hardenability, are applied for that purpose as a substitute. However, recently a nitrided hard 18-8 stainless steel products have increasingly used for such a use. These products are generally nitrided at temperatures between 550.degree. to 570.degree. C., 480.degree. C. at the lowest.
However, both the above products of a martensitic stainless steel and a nitrided hard 18-8 stainless steel have a drawback of inferior anti-corrosion compared with an unprocessed austenitic stainless steel products. As a result of a series of studies, inventors found that the anti-corrosion property of 18-8 stainless steel products deteriorated due to the following reason. Since a crystalline chrome nitride (CrN, Cr.sub.2 N and so on) is produced in a formed nitrided layer, concentration of solid soluble chrome drastically decreases. This means that active chrome disappears completely though the active chrome is indispensable to form a passive coat layer which functions to retain the anti-corrosion property of stainless steel. It is inevitable that the anti-corrosion property deteriorates when austenitic stainless steel products are nitrided. Therefore, the application range of nitriding austenitic stainless steel products to improve hardness has been limited.